Serum immunoglobulin G levels in patients with cirrhosis due to autoimmune hepatitis or other etiologies

Authors: Yu Su, Qianyi Wang, Xiaoyi Sun, Xinyu Zhao, Xinyan Zhao, Jidong Jia, Shan Shan

Abstract

Objectives:

Immunoglobulin G (IgG) elevation is a key laboratory finding of autoimmune hepatitis (AIH). However, the IgG elevation also occurs in patients with cirrhosis due to diverse etiologies. Therefore, we compared serum levels of globulin (GLB) and immunoglobulins among cirrhotic patients and optimized the IgG level to improve its diagnostic accuracy for AIH in the context of cirrhosis.

Methods

In this cross-sectional study, we included age- and gender-matched patients with cirrhosis due to AIH and non-AIH etiologies. Demographic and key laboratory profiles were compared, focusing on the levels of GLB and immunoglobulins. Receiver operating characteristic curves were constructed. Bilateral P < 0.05 and area under receiver operating characteristic curves greater than 0.5 were considered statistically significant.

Results

A total of 60 AIH patients and 259 patients with cirrhosis of non-AIH etiologies were analyzed. The AIH group exhibited higher alanine aminotransferase and aspartate aminotransferase levels. Elevations of GLB (9.8–58.3%) and IgG (47.4–97.2%) levels were observed in all groups of cirrhosis, with the highest levels of IgG, immunoglobulin M, and immunoglobulin A occurring in the patients with cirrhosis due to AIH, primary biliary cholangitis, and alcoholic liver disease group, respectively. At a cutoff IgG level of 2000 mg/dl (1.25× upper limit of normal), the sensitivity and specificity for the diagnosis of AIH cirrhosis were 81.7% and 74.1%, respectively, with an area under receiver operating characteristic curves of 0.814 (P < 0.001).

Conclusion

Hyperimmunoglobulinemia occurs in patients with cirrhosis due to different etiology. However, the different patterns of immunoglobulin subtype elevation may facilitate the differentiation of the underlying etiology of cirrhosis, with IgG level more than 2000 mg/dl (1.25× upper limit of normal) having a fair diagnostic performance for AIH-related cirrhosis.

Introduction

Hyperimmunoglobulinemia/hyperglobulinemia, elevated levels of aminotransaminases and multiple positivity of auto-antibodies are laboratory hallmarks of autoimmune hepatitis (AIH) [1–4]. Indeed, hyperimmunoglobulinemia, especially elevated serum levels of immunoglobulin G (IgG), is one of the keys to diagnosing AIH [5,6]. Therefore, serum IgG levels are listed as an important criterion in the two diagnostic scoring systems proposed by the International Autoimmune Hepatitis Group (IAIHG) [7,8]. Furthermore, normalization of IgG levels after immunosuppressive therapy is regarded as one of the key criteria of biochemical response [9,10].

However, hyperimmunoglobulinemia could also occur in patients with cirrhosis due to other etiologies [11,12]. Tomasi and colleagues reported that the percentages and elevations in gamma-globulin concentrations were higher in advanced cirrhosis [13]. Considering hyperimmunoglobulinemia is common in patients with cirrhosis of different etiology, the diagnostic value of IgG elevation for AIH is compromised in patients with cirrhosis.

Therefore, we conducted this retrospective study comparing the serum levels of globulin (GLB) and immunoglobulins among patients with cirrhosis of different etiologies to optimize the cutoff values for distinguishing AIH from other etiologies.

Methods

Study population

This was a retrospective cross-sectional study among patients with cirrhosis of different etiologies. Hospitalized patients were screened for eligibility in Beijing Friendship Hospital, Capital Medical University, from January 2002 to December 2021. This study was approved by the Medical Ethics Committee of Beijing Friendship Hospital, Capital Medical University, which granted a waiver for informed consent (Approval No. 2022-P2-229-01). The privacy rights of human subjects have been observed. All procedures followed the ethical standards of the Declaration of Helsinki of 1964, as revised in 2024.

Inclusion and exclusion criterion

Patients were included if (a) at least 18 years old; (b) meet the criteria of cirrhosis [14].

Patients were excluded if they (a) concomitant with malignancies; (b) received liver transplantation or bone marrow transplantation before diagnosis; (c) cirrhosis of unknown etiology; (d) diseases associated with the synthesis and metabolism of GLB as well as immunoglobulin, such as lymphoma, Castleman disease, plasma cell dysfunction, multiple myeloma; (e) complicated with severe abdominal or pulmonary infection, sepsis; (f) insufficient clinical data.

Diagnostic criteria for compensated cirrhosis [15] (one of the four was required)

(a) histological cirrhosis; (b) gastroesophageal varices excluding noncirrhotic portal hypertension; (c) imaging signs of cirrhosis and/or portal hypertension; and (d) meeting two or more of the four (a) platelet less than 100 × 10^9^/L without other explanations; (b) albumin less than 35 g/L excluding malnutrition or kidney diseases; (c) international ratio more than 1.3; and (d) aspartate aminotransferase-to-platelet ratio index more than 2.

Diagnostic criteria for decompensated cirrhosis [15]

(a) cirrhosis and (b) the presence of any one of the complications, including ascites, variceal hemorrhage, and hepatic encephalopathy.

The diagnostic criteria for liver diseases with different etiology

Autoimmune hepatitis

The revised IAIHG diagnostic score at least 10 points or the simplified diagnostic IAIHG score at least 6 points in patients [16]; immunosuppressive treatment naïve.

Primary biliary cholangitis

Elevated levels of alkaline phosphatase and γ-glutamyl transpeptidase, normal intra- and extrahepatic bile ducts on abdominal imaging; positivity for M2 subtype of antimitochondrial antibodies, anti-gp210 or sp100; the liver histology was compatible with or diagnostic for primary biliary cholangitis (PBC) [17].

Alcoholic liver disease

Liver disease in patients with consumption of more than three drinks per day in males and more than two drinks per day in females, or binge drinking (defined by the National Institute of Alcoholism and Alcohol Abuse as consumed more than five drinks in males and more than four drinks in females, over 2-h period). One drink is defined as a beverage containing about 14 g of alcohol, which is present in 12 ounces of beer (5% weight/volume), 5 ounces of wine (8–10% weight/volume), or 1.5 ounces of hard liquor (40–45% weight/volume) [18].

Metabolic dysfunction-associated fatty liver disease

(a) Hepatic steatosis identified by imaging techniques and/or at least 5% macrovascular steatosis by liver histology; (b) presence of at least one metabolic syndrome (i) BMI at least 24.0 kg/m^2^, or waist circumstance at least 90 cm (male)/85 cm (female), or excessive body fat content and percentage; (ii) blood pressure at least 130/85 mmHg, or undergoing antihypertensive medication therapy; (iii) fasting plasma glucose at least 6.1 mmol/L, or 2-h postprandial plasma glucose at least 7.8 mmol/L, or HbA1c at least 5.7%, or history of type 2 diabetes mellitus, or homeostasis model assessment of insulin resistance at least 2.5; (iv) plasma triglycerides at least 1.70 mol/L, or undergoing lipid-lowering medication therapy; (v) plasma high-density lipoprotein cholesterol 1.0 mmol/L (male)/1.3 mmol/L (female) or less, or undergoing lipid-lowering medication therapy; (c) exclusion of other potential etiologies of hepatic steatosis [19].

Chronic hepatitis B/chronic hepatitis C

Chronic hepatitis B (CHB) was defined as hepatitis B surface antigen persistent for at least six months with variable serum levels of HBV DNA [20,21]. Chronic hepatitis C (CHC) was defined as positive anti-HCV and HCV RNA for more than six months [22].

Demographic and baseline clinical data collection

Clinical and laboratory data were collected, including gender, age, complete blood count, liver biochemistry, prothrombin time and international ratio, immunological markers, and abdominal imaging data.

Statistical analysis

To get a more convincing conclusion, patients with cirrhosis caused by AIH and other etiologies were matched by the criteria the median age of the two groups should be less than one year, and the gender difference should be nonsignificant.

Continuous variables were expressed as median (interquartile range) or means ± standard deviations and compared with Kruskal–Wallis test. Categorical data were presented as frequencies and percentages and compared with the Chi-squared test, Fisher’s exact test, and Bonferroni method, as appropriate.

The diagnostic value of GLB and IgG levels was assessed by calculating the receiver operating characteristic (ROC) curve, with optimal cutoff values being selected to maximize sensitivity and specificity.

A two-tailed P < 0.05 after Bonferroni correction was considered statistically significant. An area under the ROC (AUROC) more than 0.5 indicated that the model performed better than random guessing. All statistical analysis was performed by SPSS (version 26.0, IBM Corporation, Armonk, New York, USA).

Results

The demographics of the study population

In total, 319 patients with cirrhosis were included in this study, with underlying etiology being AIH in 60 and non-AIH in 259 [86 PBC, 48 alcoholic liver disease (ALD), 41 metabolic dysfunction-associated fatty liver disease (MAFLD), 84 CHB/CHC] (Fig. 1). There were 32 AIH patients had liver biopsied. The median age in the AIH group was 58.0 years, and the percentage of female patients was 76.7%. In the non-AIH group, the median age was 57.0 years, and the female proportion was 66.0%. The difference in median age and gender distribution between the AIH and the non-AIH group was not statistically significant (age: P = 0.725; P = 0.111).

The clinical and laboratory characteristics of the included patients

The demographic and clinical characteristics of patients with cirrhosis due to different etiologies are shown in Table 1. Patients in the AIH group had higher alanine aminotransferase and aspartate aminotransferase levels than those in the other groups (all P < 0.001). Not surprisingly, a significantly higher level of alkaline phosphatase was found in PBC than the AIH group [145.5 (115.0–200.0) vs. 262.0 (149.8–472.0), P < 0.001]. Additionally, total bilirubin levels were significantly elevated, and albumin levels were significantly reduced in the AIH group compared with the PBC and MAFLD groups (P < 0.001).

Regarding liver function reserve, the ratio of patients in the Child B and C classes in AIH patients was higher than that in patients with other etiologies (P < 0.001) (Table 1). The median MELD score in the AIH group was higher than that in the PBC group (P < 0.01), but comparable to the other groups.

The serum levels of globulin and immunoglobulins in patients with cirrhosis of different etiologies

Not surprisingly, all patients with cirrhosis had increased levels of GLB and IgG (Table 2). However, much higher levels of GLB and IgG were presented in the AIH group than in other groups (P < 0.01) (Fig. 2a, b). At the same time, AIH patients had markedly lower levels of immunoglobulin M (IgM) than PBC [132.0 (88.4–202.5) vs. 305.0 (191.0–500.3), P < 0.001] and immunoglobulin A (IgA) levels than ALD group [366.5 (243.0–508.9) vs. 550.5 (405.0–743.8), P = 0.008].

Upon further analysis, 58.3% of AIH patients with GLB levels exceeded the upper limit of normal (ULN), which was significantly higher than other groups (Fig. 2e) (P < 0.001). Additionally, 93.2, 51.7, and 21.7% of AIH patients had IgG levels exceeding 1.0×ULN, 1.5×ULN, and 2×ULN, respectively. These proportions were significantly higher than in patients with cirrhosis of other etiologies (Fig. 2f–h) (all P < 0.001).

The serum levels of globulin and immunoglobulins in patients with cirrhosis of different etiologies stratified by liver function reserve

Next, we compared the GLB and immunoglobulin levels across patients with cirrhosis of different etiologies after stratification by compensated/decompensated status, Child-Pugh classification and MELD score (Figure S1, Supplemental Digital Content 1, https://links.lww.com/EJGH/B309). AIH patients with cirrhosis still presented the highest levels of GLB and IgG, whereas the patients with PBC and ALD still had the highest levels of IgM and IgA, respectively.

The serum levels of globulin and immunoglobulins in autoimmune hepatitis patients with cirrhosis stratified by liver function reserve

As shown in Fig. 3, AIH patients with compensated cirrhosis had lower IgA levels than those with decompensated cirrhosis [280.0 (206.5–411.5) vs. 415.0 (279.0–580.0), P = 0.011] (Fig. 3a, b). However, AIH patients with compensated and decompensated cirrhosis exhibited comparable levels of GLB, IgG, and IgM (all P > 0.05).

When stratified by the Child-Pugh classification, GLB, IgG, and IgM levels were not significantly different among patients with Child-Pugh A and B/C class. However, IgA levels were lower in Child-Pugh A patients compared with the other groups [237.0 (197.5–355.5) vs. 387.0 (274.0–522.0), P = 0.034] (Fig. 3c, d). Nevertheless, upon further stratification of AIH patients into MELD 14 or less and MELD more than 14, the GLB and immunoglobulin levels were comparable (all P > 0.05) (Fig. 3e, f).

The diagnostic performance of globulin and immunoglobulin G to discriminate autoimmune hepatitis from other chronic liver disease

We attempted to find the optimal cutoff values of GLB and IgG for differentiating patients with cirrhosis due to AIH or other etiologies. A cutoff value of 40.1 g/L for GLB yielded a sensitivity of 56.8% and a specificity of 82.7% for differentiating AIH from other etiologies, with an AUROC of 0.758 (P < 0.001). Furthermore, a cutoff value of greater than 2000 mg/dl (1.25×ULN) for IgG observed a sensitivity of 81.7% and specificity of 74.1% for differentiating AIH from other etiologies, with an AUROC of 0.814 (P < 0.001), the positive and negative predictive values were 48.0% and 93.4%, respectively (Fig. 4). In the subgroup of patients with liver biopsy-confirmed AIH, an IgG threshold of 1800 mg/dl helped to distinguish AIH from other etiologies with 88.0% sensitivity and 62.3% specificity (AUROC 0.798). The corresponding positive and negative predictive values were 23.2 and 98.4%, respectively (Figure S2, Supplemental Digital Content 1, https://links.lww.com/EJGH/B309).

Discussion

Our study demonstrated that increased levels of GLB and immunoglobulins were prevalent in patients with cirrhosis due to different etiologies. However, AIH patients with cirrhosis exhibited significantly higher elevations of GLB and IgG than those with cirrhosis due to other etiologies. The thresholds of IgG more than 2000 mg/dl (1.25×ULN) or GLB > 40.1 g/L were suggestive of AIH-induced cirrhosis.

Our current study confirmed that patients with cirrhosis due to different etiologies exhibited increased GLB levels, ranging from 9.8 to 58.3%, and each group displayed elevated IgG with varying frequencies (47.4–93.2%). This result aligns with prior studies, where 75% of CLD groups presented various degrees of elevated hypergammaglobulinemia [23]. The mechanisms underlying elevated serum immunoglobulin levels in cirrhosis have not been fully elucidated but may involve excessive stimulation of B lymphocytes by gut-derived antigens [24]. Structural changes in intestinal mucosa allow the translocation of bacteria and their products into the circulation, thereby contributing to this process [25,26].

We also confirmed that patients with cirrhosis of different etiologies had different patterns of immunoglobulin elevation. Indeed, the PBC group demonstrated the highest IgM levels, and the ALD group had the highest IgA levels, whereas the AIH group had the highest level of IgG, consistent with previous reports [27–29]. We also found that the immunoglobulin levels in MAFLD patients were lower than those in the other four groups, failing to confirm the previous reports on the correlation between elevated serum IgA levels and advanced fibrosis in MAFLD [25,30]. Overall, these results support the notion that the elevation of different immunoglobulin subtypes may help differentiate the etiology of cirrhosis.

Importantly, we found that nearly all patients with AIH-related cirrhosis exhibited increased IgG levels, with 81.7% exceeding 2000 mg/dl, in contrast to 22.2% in patients with non-AIH cirrhosis. These findings align with those reported by Hind and colleagues [23]. Furthermore, no significant differences in GLB and IgG levels were observed among patients with AIH cirrhosis strategies by liver function reserve, consistent with the study by Sharma and colleagues [31]. This finding may be partially explained by the hypothesis that in patients with AIH, the elevated Ig G level is mainly due to loss of self-tolerance where autoantigen-activated T cells produce cytokines that persistently stimulate auto-antibodies production by B lymphocytes [32,33].

Finally, we demonstrated that for the diagnosis of AIH cirrhosis, at the cutoff value of 2000 mg/dl (1.25×ULN) for IgG, the sensitivity and specificity were 81.7% and 74.1%. Of note, this cutoff of IgG value in our study is much lower than that reported by Hind and colleagues (3000 mg/dl) [23]. Whether this difference is due to patients’ ethnic differences or other unknown factors needs further investigation. This finding might help to identify AIH among various etiologies, especially in scenarios where percutaneous liver biopsy is not feasible due to severe coagulopathy, thrombocytopenia, or massive ascites.

There are several limitations in our study. First, this is a single-center, retrospective cross-sectional study included a relatively small number of patients. Second, the uneven distribution of patient numbers across different etiology groups potentially introduces bias. Nonetheless, we endeavored to match AIH patients with other groups by age and gender to mitigate these limitations. Thirdly, the absence of liver biopsy in a subset of patients might introduce some diagnostic uncertainty; however, all these AIH patients satisfied the revised IAIHG score requirements.

Conclusion

In summary, increased GLB and IgG levels were common among patients with cirrhosis of different etiologies. Nevertheless, the elevation of different immunoglobulin subtypes may facilitate the differentiation of the underlying etiology of cirrhosis. Specifically, IgG level more than 2000 mg/dl (1.25×ULN) may help to identify AIH-related cirrhosis.

Acknowledgements

None.

This work was supported in part by a grant from the National Natural Science Foundation of China (No. 82270603 and 82400720).

J.J. and S.S. performed study concept and design; Y.S., X.S., and X.Z. provided acquisition of data; X.Z. provided statistical aids; Y.S. performed writing, provided statistical analysis and interpretation of data; Q.W., S.S., and J.J. performed critical review and revision of the paper. All authors read and approved the final paper.

This study was approved by the Medical Ethics Committee of Beijing Friendship Hospital, Capital Medical University, which granted a waiver for informed consent (Approval No. 2022-P2-229-01). The privacy rights of human subjects have been observed. All procedures followed were in accordance with the ethical standards of the responsible committee on human experimentation (institutional and national) and with the Helsinki Declaration of 1975, as revised in 2024.

Conflicts of interest

There are no conflicts of interest.

Supplementary Material